Pasta filata cheese, particularly mozzarella cheese, is one of the growing categories of cheese. It is primarily used in cooking and is the preferred cheese for pizza due to the stretchiness associated with pasta filata cheese when such cheeses are heated. Pasta filata cheeses are also used as a snack food in the form of short sticks, popularly called "string cheese". Regular full fat mozzarella cheese is medium firm with a clean, slightly acid cheese flavor. The cheese melts and becomes stringy upon cooking. When fat is removed from milk and the mozzarella cheese produced therefrom contains less than about 6% fat, the cheese becomes dry, firm, inelastic, does not flow when melted and has poor stretch qualities.
A conventional method for the manufacture of pasta filata cheese, such as mozzarella, is described in Kosikowski, F., "Cheese and Fermented Milkfoods", 1966, Edwards Brothers, Inc., Ann Arbor, Mich., pp. 162-167. In the method described by Kosikowski, standardized milk is pasteurized and cooled to a temperature of about 90.degree. F. A starter culture is added with sufficient rennet to coagulate the milk in about thirty minutes. The resulting coagulum is cut to provide pieces of curd in whey. The cut curds are set in the warm whey for about 15 minutes with periodic gentle agitation. The curds in the whey are pushed to the back of the vat and the free whey is removed from the vat. Whey removal is slower than that for cheddar cheese because of a lack of cooking and the acidity. As the whey departs, the curds are packed gently together. The large curd packs are cut into blocks to effect quicker cooling. The curd blocks are rinsed with cold water and immersed in cold water. The cold water is drained after 15 minutes and the curds are bundled into clean cheese cloth to make 45 to 60 lb. bundles. The curd bundles are placed in a chill room (40.degree. F.) to effect further draining of curd. The whey drains from the curd bundles overnight in the chill room. The curd, at this point, is referred to as raw curd. The drained curd bundles are removed from the chill room and acid ripening is commenced by exposing the drained curd bundles to warmer room temperatures for a period of at least one day. The curd bundles are removed from the warm room after complete drainage and after the curd pH decreases to a level of 5.2 to 5.4.
The cloth is removed from the acidified raw curd and the curd bundle is chopped into small pieces. these pieces are placed in hot water or hot whey at a temperature of about 180.degree. F. in a mechanical blender. The hot water covers all the curd by a few inches. The curds are left in the hot water for a few minutes but not long enough for them to exceed a temperature of 135.degree. F. A gentle molding agitation is then started with a mechanical apparatus which is used to pull and stretch the raw curd into a smooth, white plastic mass. The hot plastic mass is packed into suitable molds. Later, the cheeses are immersed in a salt brine for a period of about 24 hours. The cheese is then dried in air and is wrapped and packaged for shipment.
Numerous attempts have been made to provide improved methods for the manufacture of pasta filata cheese wherein the working and stretching of the raw curd is supplanted by continuous mechanical methods. U.S. Pat. No. 3,692,540 to Mauk describes a method for the manufacture of pasta filata cheese wherein the curd is held in whey to acid condition the curd. The curd is held until the acidity of the whey is from 0.25 to 0.30%. The raw curd is divided into pieces and the curd pieces are heated without working in a process cheese cooker to a temperature of 130.degree.-160.degree. F. The method of the Mauk patent utilizes a final direct heating step without working or stretching the cheese curd.
U.S. Pat. No. 3,117,008 to Mauk teaches a method for the manufacture of pasta filata-type cheeses wherein final curd texture is achieved by curing the curd for a period of time sufficient to provide a cheese having a smooth and continuous texture. In the method, a pasta filata curd, which includes acid-producing agents, is cooked at a temperature below that at which the acid-producing agents are substantially inactivated. Thereafter, the curd is leached to remove acid and provide an acidity of less than about 0.8%. The curd is then pressed and the pressed curd is subjected to vacuum conditions to close the curd. Thereafter, the curd is cured and the curing process provides a cheese having a smooth and continuous texture through the development of acidity by the acid-producing agents.
U.S. Pat. No. 3,531,297 to Kielsmeier, et al. is directed to a process for making pasta filata cheese wherein pasta filata cheese curd is subjected to particular treatment to make it more suitable for the steps of the pasta filata cheese-making process which follow cheddaring, including heating the curd particles by contact with heated water to a temperature in the plastic temperature range of the curd while mixing and stretching the curd. The Kielsmeier, et al. patent teaches that the mixing and stretching may be continued under superatmospheric pressure while forcing the curd through a restricted backpressure-creating outlet.
U.S. Pat. No. 4,898,745 to Zamzow, et al. is directed to a method for making pasta filata cheese from a pasta filata curd produced by any of the conventionally known methods. The curd is divided into pieces and the pieces are delivered to an auger conveyor. The curd is heated and worked in the auger conveyor to a plastic consistency as it passes through the conveyor. Plastic curd is transported through a steam injection heating zone and a static mixing zone to provide a homogeneous molten curd. The molten curd is transferred from the mixer through a holding conduit into a vacuum chamber so as to flash-cool the molten curd. The molten curd is pasteurized in the holding conduit to provide a pasta filata cheese with improved storage properties.
While any of the conventionally known methods described above can be used to produce a pasta filata cheese having desired melting and stretch properties from full fat milk or partially defatted milk, these methods have been found to be unsuitable to provide a pasta filata cheese from low fat or skim milk wherein the resulting cheese has less than about 6% fat.
Accordingly, it is an object of the present invention to provide a method for making pasta filata cheese. It is an another object of the present invention to provide a method for making pasta filata cheese from low fat milk or skim milk that retains the stretch properties associated with full fat or partially defatted milk having more than about 6% fat in the finished cheese.